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This invention relates to electric fuel pumps used to supply fuel to internal combustion engines, and more particularly to a cartridge insertable in the inlet of a variety of such pumps to provide a relief valve assembly for the pumps. At low pressures (12 psi or less) such as occur in carbureted engine applications, the relief valve also acts as a pressure regulator. At higher pressure applications such as found in fuel injected engines, the valve acts to relieve excess pressure in the fuel rail between the fuel pump and engine should the pressure regulator in the rail fail, or if a fuel line becomes kinked or is otherwise blocked.
Electric fuel pumps are well-known in the art. The pump has an inlet side in which fuel is drawn into the pump at low pressure. The pump then has one or more pumping stages by which the fuel pressure is elevated to a significantly higher level. Finally, the pump has an outlet stage through which the pressurized fuel is delivered to an internal combustion engine, typically a fuel injected engine, requiring fuel at high pressure for proper operation. As noted, the fuel pumps are also usable in carbureted engine applications. The fuel pump can be mounted either inside or outside the fuel tank. Electric fuel pumps include a relief valve for directing fuel back to a fuel tank in which the pump is installed. In many pump constructions, the relief valve assembly is mounted in the inlet portion of the pump, and the fuel returned back to the inlet side of the pump through the relief valve is high pressure fuel from the outlet side of the pump.
It will be appreciated that there are wide variety of fuel pumps for different engine applications. The pumps are of different sizes and shapes and their outlet pressures vary over a wide range; i.e., from 100 psi or greater, to less than 10 psi. Because of this diversity, it is commonplace in manufacturing a line of fuel pumps for a manufacturer to have to stock a large number of different parts for use in their production. This makes inventory costs very high and can be particularly expensive because a few part numbers usually represent the vast portion of the sales volume; yet, many more part numbers must be made and stocked to complete the product line. The ability to utilize a single component throughout much of the product line would create significant cost savings. The impact would be not only in inventory costs, but also in production because fewer fixtures would be required, and less setup changes and machining operations would be involved in changing from one part number to another.
The present invention is directed to a relief valve assembly for electric fuel pumps. The assembly includes a molded plastic cartridge in which components of the relief valve are housed. The cartridge is readily inserted in the inlet porting plate of a wide variety of fuel pumps to direct high pressure fuel from the outlet side of the pump back to the inlet side of the pump. Using different springs within the cartridge allows the relief valve to be modified for use in pumps operating at different pressures. This can also be accomplished by changing the size of the inlet orifice of the cartridge. The combination of spring weights and orifice sizes enables a relief valve of a common design to be used in a variety of different pumps.
The housing of the cartridge is designed to readily fit into a porting plate so to simplify manufacture of a pump. Preferably, the cartridge is made of a light weight, slotted plastic material which is impervious to fuel varnish buildup which causes sticking of the relief valve. Slotting allows the cartridge to easily bypass fuel back to the inlet side of the pump when the relief valve is opened. The cartridge is color coded for ease of identification. Since the relief valve components are self-contained within the cartridge, they are readily tested prior to installation into a pump.
Other objects and features are in part apparent and in part pointed out hereinafter.